The Doctor looks up from a book he is reading and tells sidekick Amy Pond: “I always rip out the last page, I don’t like endings.”

However fans watching tonight’s Doctor Who finale will already know Amy is leaving because it’s been in the news for weeks. We just don’t know how.

But whatever the outcome, the usual hiding behind the sofa is likely to take a back seat to breaking down in tears as Amy, played by Karen Gillan, and husband Rory Williams, played by Arthur Darvill, depart.

Karen struggled to cope emotionally after filming those final moving scenes as a companion to Matt Smith’s Doctor in the hit BBC sci-fi series.

“I just can’t believe it’s real,” says the actress, 24.

“I have just always thought in my head I am in the show until the final episode airs, so I thought I had loads of time. But now it is approaching.

“It is a really weird sensation because I can’t wait to see the episode and can’t wait for everyone else to see it – but I don’t want it to air at the same time.

“I was emotional for about two weeks filming the episode and I was crying at everything. Things that weren’t even sad, anything would set me off.

“Everything was already bubbling under the surface. So in my final scene it is not even acting, it is real because I knew I had to leave in real life and I had to leave Matt and Arthur.

"It was something that came really naturally.”

First appearance: Karen as a policewoman (Image: BBC)

Karen decided she wanted to leave last year and discussed and finalised her exit over dinner with show boss Steven Moffat.

Karen is keeping tight lipped about what exactly happens but says she’s delighted about Amy’s last adventure being against terrifying foe the Weeping Angels.

“It was hard to film at points because I was getting nostalgic,” says Karen.

“I kept thinking ‘this is the last time I will do this or that’. But I couldn’t have asked for a better way to go, it is so good.

“All I wanted was for her to go out in flames of burning glory. I definitely think she does that.”

Karen, from Inverness, joined the show along with Smith, 29, in a blaze of publicity in May 2009 which included a tour of the Mirror newsroom.

When I met her for their first interviews together she was slightly nervous and even giggly but over the years she has matured both in interviews and on screen.

“It changes your life so much,” she says of the show, which attracts up to eight million viewers.

“I have been through so many extreme experiences. It can’t help but make you a little bit older.

“And I am so much more confident. I was like a rabbit in headlights when I started. I was like ‘what is this’.

“I was 21 and had never done it before. You evolve with it and go with it. I feel like I can handle it now a lot more.”

Farewell: The Doctor Matt Smith hugs the departing stars (Image: BBC)

The success – she’s now in big demand as an actress – has required a huge sacrifice with her love life.

When the show started Karen was dating photographer Patrick Green.

The long-term relationship ended in January and since then she has only been pictured cuddling co-stars including actor Andrew Brooke on the Doctor Who set, and Stanley Weber, a co-star in new film Not Another Happy Ending.